The present invention relates to high purity poly(3-aminopropylmethylsiloxane)-poly(dimethylsiloxane) copolymers and a method for their preparation. More specifically, the present invention relates to more than 95% isomerically pure poly(3-aminopropylmethylsiloxane)-poly(dimethylsiloxane) copolymer fluids, both linear and cyclic, prepared by the base catalyzed polymerization and ring-chain equilibration of a mixture of at least 95% isomerically pure poly(3-aminopropylmethylsiloxanes) and dimethylcyclosiloxanes. These poly(3-aminopropylmethylsiloxane)-poly(dimethylsiloxane) copolymers have utility as intermediates for other derivative poly(organofunctionalsiloxanes) and in cosmetic, textile, and automotive applications, and as coatings and adhesives.
There is considerable prior art relating to the synthesis of poly(aminoalkylmethylsiloxanes). Generally, poly(aminoalkyl-methylsiloxanes) have been produced by first preparing aminoalkylmethyldialkoxysilanes, followed by hydrolysis with or without an endblocking agent, such as a trimethylsilyl derivative, forming cyclic and linear poly(3-aminoalkylmethylsiloxanes). The isomeric purity of the poly(aminoalkylmethylsiloxane) fluids, prepared in the manner of the prior art, is dependent upon the isomeric purity of the aminoalkylmethyldialkoxysilane prepared in the first step of the synthesis.
German Patent No. 2408480 describes the reaction of a silazane derivative from allylamine and an organohydrochlorosilane, in the presence of a proton acceptor to form an intermediate silazane which then undergoes a hydrosilylation reaction catalyzed by a platinum catalyst. Upon alcoholysis, the intermediate hydrosilylation product forms 3-aminopropylmethyldiethoxysilane in 70% overall yield. A molar excess of at least 50% of allylamine is used in this process. Identification of the beta-isomer in the product was not made. Japanese Patent No. 10017578 describes another method of synthesis by hydrosilylation of N,N-bis(tri-methylsilyl)allylamine by methyldimethoxysilane. The product of that reaction is then heated with methanol to form 3-aminopropylmethyldimethoxysilane in at least 85% overall yield. The presence of the beta-isomer in the product was not identified. Japanese Patent No. 11209384 describes the use of a rhodium:cyclooctadiene complex as a hydrosilylation catalyst for the addition of methyldiethoxysilane to allylamine to form 3-aminopropylmethyldiethoxy-silane in 78% yield. 2-Aminopropylmethyldiethoxysilane is formed in very low levels in this process not exceeding 0.5%.
U.S. Pat. No. 5,391,675 describes the formation of an aminopropylmethylsiloxy-containing polydimethylsiloxane by barium or strontium hydroxide catalyzed condensation of a silanol terminated polydimethylsiloxane with a 3-aminopropylalkoxysilane with elimination of an alcohol.
High isomeric purity poly(3-aminopropylmethylsiloxane)-poly(dimethylsiloxane) copolymers are not items of commerce, although it is noted that Gelest Reactive Silicones has a catalog which lists aminopropylmethylsiloxane-dimethylsiloxane copolymer but does not mention its method of preparation or its isomeric purity. Mention is also made that N-Methyl- and N,N-Dimethylaminopropylmethylsiloxane and -aminoisobutyl-methylsiloxane containing polydimethylsiloxane copolymers are known in the art.
The present invention provides near quantitative yields of greater than about 95% isomeric purity of poly(3-aminopropylmethylsiloxane)-poly(dimethylsiloxane) copolymers of the general formulae
xe2x80x83Me3SiO(H2NCH2CH2CH2MeSiO)w(Me2SiO)xSiMe3
(H2NCH2CH2CH2MeSiO)y(Me2SiO)z
wherein Me is methyl, w may range from 1 to about 100 or more, x may range from 1 to about 100 or more, y may range from 1 to about 6, z may range from 1 to about 6, and y+z may range from 3 to about 7.
The present invention also provides a simple method for rapidly producing poly(3-aminopropylmethylsiloxane)-poly(dimethylsiloxane) copolymers of the general formulae:
Me3SiO(H2NCH2CH2CH2MeSiO)w(Me2SiO)xSiMe3
(H2NCH2CH2CH2MeSiO)y(Me2SiO)2
wherein Me is methyl, w may range from 1 to about 100 or more, x may range from 1 to about 100 or more, y may range from 1 to about 6, z may range from 1 to about 6, and y+z may range from 3 to about 7, the method comprising heating of poly(3-aminopropylmethylsiloxane) of at least 95% isomeric purity, with a basic catalyst, and a dimethylcyclosiloxane, such as octamethylcyclotetrasiloxane or decamethlcyclopentasiloxane.
The present invention provides near quantitative yields of greater than about 95% isometric purity of poly(3-aminopropylmethylsiloxane)-poly(dimethylsiloxane) copolymers of the general formulae:
Me3SiO(H2NCH2CH2CH2MeSiO)w(Me2SiO)xSiMe3
(H2NCH2CH2CH2MeSiO)y(Me2SiO)z
wherein Me is methyl, w may range from 1 to about 100 or more, x may range from 1 to about 100 or more, y may range from 1 to about 6, z may range from 1 to about 6, and y+z may range from 3 to about 7. The present invention also provides high purity poly(3-aminopropylmethylsiloxane)-poly(dimethylsiloxane) copolymers which are greater than about 97% free of dimethylcyclosiloxanes and are substantially free of other organic and inorganic compounds.
The ratio of linear to cyclic polymers in the fluids of the present invention can vary widely, but are typically in the range of from about 1:10 to about 10:1.
The present invention also provides a novel method for producing the high isomeric purity poly(3-aminopropylmethylsiloxane)-poly(dimethylsiloxane) copolymers of the present invention, the process comprising (a) mixing poly(3-aminopropylmethylsiloxane) of at least about 95% isomeric purity, with a cyclodimethylsiloxane of the general formula (Me2SiO)a wherein Me is methyl and xe2x80x9caxe2x80x9d may range from 3 to about 7, and a basic catalyst, (b) heating the mixture to polymerize the cyclodimethylsiloxane to poly(dimethylsiloxane) and to copolymerize the poly(3-aminopropylmethylsiloxane) with the formed poly(dimethylsiloxane), and (c) decomposing the catalyst and recovering the product copolymer.
The high isomeric purity poly(3-aminopropylmethylsiloxane) is prepared according to the instructions set forth in a co-pending concurrently filed commonly assigned United States patent application by the same inventors Ser. No. 09/532,714.
The dimethylcyclosiloxanes are well known to those of ordinary skill in the art, and are preferably of the formula
(Me2SiO)a
wherein Me is methyl and a is from 3 to about 7. Preferred dimethylcyclosiloxanes for use in the practice of the present invention are octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane and mixtures thereof.
The basic catalysts that are known in the art to facilitate copolymerization of cyclodimethylsiloxanes and poly(3-aminoorganomethylsiloxanes) include most metal hydroxides, metal oxides, quaternary organoammonium hydroxides, quaternary organophosphonium hydroxides, and metal trimethylsilanolates. The preferred catalysts are quaternary organoammonium hydroxides, quaternary organophosphonium hydroxides, and metal trimethylsilanolates. A particularly useful catalyst for the based catalyzed polymerization and ring-chain equilibration is tetramethylammonium hydroxide. The catalyst is typically employed in amounts ranging from about 100 ppm to about 10,000 ppm, preferably from about 1000 to about 5000 ppm, and more preferably from about 2000 to about 4000 ppm, based on the weight of the poly(3-aminopropylmethylsiloxane) and cyclodimethyl-siloxane.
The copolymerization can be carried at temperatures ranging from about 50xc2x0 C. to about 150xc2x0 C., preferably between about 60xc2x0 C. and 100xc2x0 C. and more preferably between 80xc2x0 C. and 120xc2x0 C., in the presence of the basic catalyst.
The catalyst may then be decomposed and the decomposition products thereof driven from the copolymer by further heating, such as to a temperature in the range of from about 130xc2x0 C. to about 160xc2x0 C.